The Carolina Population Center proposes a 5-year program project to study the interrelationship between health and reproduction dynamics and social change in selected developing countries, beginning in China and the Philippines. Seven individual subprojects examine various aspects of health and reproduction jointly or separately. The program project uses 2 unusually rich longitudinal data sets collected for the purpose of analyzing a set of issues concerning fertility and health. Detailed anthropometric, dietary, and related health data, as well as clinical data in China are collected from individuals, with a focus in the Philippines study on women and children and in China on preschoolers and adults of reproductive age. Demographic, economic, and sociological data are being obtained by questionnaire. The data include detailed information on lactation, pregnancy and pregnancy outcome. Additional health service use and health status data are collected by questionnaire. Detailed surveys from health and family planning facilities, food markets, and key community informants provide information to supplement these data. The 7 projects are supported by 3 cores: administration, data, and statistical. The Philippines project is conducted in collaboration with the Office of Population Studies, University of San Carlos, Cebu City Philippines, and the China projects are in collaboration with the Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medicine, Beijing. The individual subprojects share a number of common elements. These include the integrated modeling of behavioral relationships in the context of biological constraints (or vice versa for the more biologically oriented projects); use of advanced statistical methods to deal with the simultaneity of many relationships, the time sequencing of key relationships, and the longitudinal nature of the analytic approaches. The projects are interdisciplinary in all stages from design and collection of data to modeling and analysis.